When two electronic devices are fixedly connected to each other, a method of using a dedicated connection mechanism is known. FIG. 8 is a view explaining a conventional example of a connection mechanism for fixedly connecting electronic devices to each other. In the example of FIG. 8, a connection mechanism 530 for fixedly connecting a first electronic device 510 and a second electronic device 520 to each other is shown. In addition to fixedly connecting the first electronic device 510 and the second electronic device 520 to each other, the connection mechanism 530 also has a function of protecting the interiors of electronic devices by preventing water from penetrating through a connection portion thereof. Meanwhile, the first electronic device 510 and the second electronic device 520 are shown in a state where lids of housings thereof are removed.
The first electronic device 510 has a terminal block 511 therein and the second electronic device 520 has a terminal block 521 therein, and the first electronic device 510 and the second electronic device 520 are electrically connected to each other by a wiring 540. The connection mechanism 530 is provided with a wiring hole allowing the wiring 540 to pass therethrough.
The connection mechanism 530 includes a first piping connector 531 configured to be connected to the first electronic device 510, a second piping connector 532 configured to be connected to the second electronic device 520, and a nut 533 for connecting the first piping connector 531 with the second piping connector 532.
FIG. 9A and 9B are views showing a structure of the conventional connection mechanism 530, in which FIG. 9A is a perspective view thereof and FIG. 9B is an exploded perspective view. The nut 533 is configured so that a female threaded portion 533a is formed up to the middle of a through-hole thereof and the opposite side is formed to have a diameter smaller than that of the female threaded portion. The smaller diameter portion servers as a slide hole 533b. 
The first piping connector 531 has a wiring hole provided therethrough and is provided with a male threaded portion 531a configured to be fastened to a female threaded portion formed in the first electronic device 510, a hexagonal fastening portion 531b allowing fastening to be performed with a tool when being fastened to the first electronic device 510, and a male threaded portion 531c configured to be fastened to the female threaded portion 533a of the nut 533.
The second piping connector 532 has a wiring hole provided therethrough and is provided with a male threaded portion 532a configured to be fastened to a female threaded portion formed in the second electronic device 520, a hexagonal fastening portion 532b allowing fastening to be performed with a tool when being fastened to the second electronic device 550, a guide portion 532c configured to be guided by the slide hole 533b of the nut 533 in an axial direction thereof, and a flange portion 532d having a diameter larger than that of the slide hole 533b and serving as a stopper for preventing the nut 533 from failing off. The diameter of the flange portion 532d is formed to be smaller than the diameter of the female threaded portion 533a of the nut 533, and thus by tightening the nut 533, the flange portion 532d is urged in a direction of the first piping connector 531, so that the second electronic device 520 can be fixed at a certain angle about an axis.
FIG. 10 is a view explaining procedures when the connection mechanism 530 fixedly connects the first electronic device 510 and the second electronic device 520 to each other. In this case, it is assumed that the second electronic device 520 is connected to the first electronic device 510 which has already been installed. Also, it is assumed that the second electronic device 520 requires an angular adjustment about the axis during connection. For example, this corresponds to a case where the second electronic device 520 has a communication antenna and is fixed in an orientation providing a good communication state, or a case where an exactly horizontal or vertical state thereof is required due to the interior structure thereof, and the like.
First, the first piping connector 531 is fastened to the first electronic device 510, and the second piping connector 532 passes through the nut 533 and then is fastened to the second electronic device 520. At this time, a tool, such as a wrench, suitable to a size of the hexagonal fastening portion 531b of the first piping connector 531 and the hexagonal fastening portion 532b of the second piping connector 532 is used.
The second electronic device 520 is moved close to the first electronic device 510 and then the second electronic device 520 is positioned at an angle about the axis. Also, while the angle is kept, the female threaded portion 533a of the nut 533 is fastened to the male threaded portion 531c of the first piping connector 531. At this time, a tool, such as a wrench, suitable to a size of the nut 533 is used. Thus, the first electronic device 510 and the second electronic device 520 are fixedly connected to each other by the connection mechanism 530.
FIG. 11 is a sectional view showing the first piping connector 531 and the second piping connector 532 fixedly connected by the connection mechanism 530. Herein, O-rings are used to keep waterproof property of connection portions. Specifically, an O-ring 534a is used to ensure waterproof property between the first electronic device 510 and the first piping connector 531, and an O-ring 534b is used to ensure waterproof property between the second electronic device 520 and the second piping connector 532. Also, an O-ring 534c is used to ensure waterproof property between the first piping connector 531 and the second piping connector 532.